Decrease in life of an optical apparatus such as LCD panels and polarization plates has become increasingly a serious problem in recent years as they are used in LCD projector operated at high brightness and high contrast. To cope with this problem, each of the polarization plates is supported by a transparent substrate having an anisotropic refractive-index, such as a single-crystalline sapphire substrate or quartz substrate that has a good thermal conductivity (heat dissipation property).
Japanese Patent Application Laid Open No. 2001-272671 discloses an LCD projector equipped with an optical system for providing illumination light, an electrooptic apparatus for modulating the light provided by the optical system based on picture information, and a projection system for projecting beams of light modulated by the electrooptic apparatus. The electrooptic apparatus has a substantially rectangular single-crystalline sapphire substrate and a polarization plate mounted on the single-crystalline sapphire substrate on at least the light incidence side or light emitting side of the electrooptic apparatus. The single-crystalline sapphire substrate, substantially rectangular in shape defined by substantially two orthogonal sides, has an optically anisotropic crystalline axis known as C axis that is substantially parallel with a substrate surface and inclined at an angle of about 3 to 7 degrees with respect to one of the two substantially orthogonal sides. Said one side is called a reference side.
In order to extend the life of these polarization panels that constitute the electrooptic apparatus together with the LCD panels, it may be considered useful to provide a highly transparent auxiliary polarization plate between each LCD panel and the polarization plate on the light emitting side of the LCD panel.
Unfortunately, however, inclination of C axis (or Z axis in the case of sapphire single crystal) of a highly transparent auxiliary polarization plate on the light emitting side has more influence on the display performance of the LCD panel than that of the aforementioned ordinary polarization plate. For example, the inclination is often a source of color irregularity on a supposedly black screen and/or a source of contrast loss of a picture.